Modern utility vehicles perform various functions in fields including agriculture, construction, road and lot maintenance, mining, surveying, and others. In many activities related to such fields, some vehicle operations tend to be repetitive. While this discussion pertains to all such fields and vehicles used therein, for clarity and brevity, the discussion herein will focus on agricultural vehicles for illustration and explanation.
Operating agricultural vehicles such as tractors, harvesters and the like can involve such repetitiveness. For instance, when plowing or planting a field, an operator must make repeated passes across a field, which may be of significant area (e.g., acreage, etc.). Due to the repetitive nature of the work and irregularities in the terrain, gaps and overlaps in the rows of crops can occur. This can result in damaged crops, overplanting, or reduced yield per acre. As the size of agricultural vehicles and farming implements continues to increase, precisely controlling their motion becomes more important.
Guidance systems are increasingly used for controlling agricultural and environmental management equipment and operations such as road side spraying, road salting, and snow plowing where following a previously defined route is desirable. This allows more precise control of the vehicles than is typically realized than if the vehicle is steered by a human. Many rely upon furrow followers which mechanically detect whether the vehicle is moving parallel to a previously plowed plant furrow. However, these guidance systems are most effective in flat terrain and when detecting furrows plowed in a straight line. Additionally, many of these systems require factory installation and are too expensive or inconvenient to facilitate after market installation.
Further, almost all utility vehicles and machines used in agricultural and similar activities are characterized by some amount of discrepancy in the positioning of its steering control (e.g., a steering wheel), with respect to the actual direction the wheels of the vehicle are oriented towards therewith. This discrepancy is commonly referred to as “play” in the steering mechanism, which can be characterized by a dead band in coupling the steering wheel to the vehicle's wheels. The term “dead band” or steering play refers to the fact that there is no change in the position of the guidance wheel touching the ground as the steering wheel is moved. The range of this dead band can vary from vehicle to vehicle, e.g., from tractor to tractor. Such steering play can adversely affect the performance of guidance systems. This is especially noticeable when reversing the direction in which the steering wheel is turned (e.g., if the steering wheel has been turned to the right and then reversed to turn the vehicle to the left). Additionally, some vehicles may exhibit more steering play when the steering wheel is turned in one direction than they exhibit when the steering wheel is turned in the other direction. As a result, a steering bias may be introduced in vehicle guidance systems because the steering play is not fully compensated for in one direction and over-compensated for in the other.
Steering play is frequently related to a sum of various mechanical alignments, adjustments, slow and cumulative mechanical changes, such as are associated with loosening, wear and tear on linkages, hydraulic actuators, valves, leakage and pressure changes, etc. Steering play is thus typically more pronounced in older vehicles than in newer ones. Further, older vehicles typically wear, loosen and otherwise change position at faster rates than newer ones. Thus, steering play in older vehicles may increase after relatively shorter operational periods and/or lighter operational duty.
Such play can cause variation and/or errors in positioning the vehicle for one or more of many repetitive operations. Such variation requires correction, which can occupy an operator's attention and efforts, such as for manual compensation, adjustment of a guidance system, etc. Occupying the operator's attention can distract the operator, which can have concomitant negative safety and economic effects. Occupying the operator's efforts makes operating the vehicle more strenuous or troublesome than it would otherwise be.
Further, such errors can cause consequences such as that some portions of land to be subject to the vehicle's activity are actually missed, and others are unnecessarily exposed to repetition thereof. Both such consequences can have negative economic and other effects. For instance, where a portion of crops is missed by plow, seed, fertilizer, pesticide, etc., that portion may be unproductive, or the vehicle's activities may need to be repeated (or substituted with other activity, e.g., corrective manual activity or activity of another vehicle) to cover the missed portion. Unnecessary exposure of another region, e.g., proximate to the missed portion, can occur with such repetition, which can be wasteful and/or harmful. Some economic cost typically inheres with the repetition itself. And for instance, where excess seed, fertilizer, pesticide, etc. is inadvertently (e.g., inaccurately, mistakenly, etc.) applied to a previously covered region proximate to the missed portion, crops can be less productive or barren in that proximate region.